The balance boards known from the existing art serve, inter alia, as input devices for computer games. These balance boards are often used, for example, in computer games in which sports such as skateboarding, snowboarding, or surfing are simulated.
A further application sector of balance boards is utilization as a training or rehabilitation device with which users can practice balance and the coordination of certain motion sequences. These training or rehabilitation devices are usually not designed for use in conjunction with a computer, and therefore also do not possess sensor apparatuses for the generation of sensor signals that can be further processed by a computer.
Apparatuses for balance exercises and balance games (balance boards) are sufficiently known in the existing art. The following documents are closest to the invention presented here:
US 2008/0261696 A1 discloses an apparatus for sensing weight displacements and jumping motions of a user. It encompasses a support surface that is mounted on four supporting feet. Beam-shaped spring elements are arranged respectively between the support surface and the four supporting feet. In the context of the greatly limited deformability of these spring elements, the support surface is tiltable relative to the supporting feet around two horizontal, mutually orthogonal spatial axes X and Y, and mounted movably along a vertical spatial axis Z orthogonal to the spatial axes X and Y.
Attached onto each of the beam-shaped spring elements are strain gauges that sense the deformation of the spring elements. Weight displacements and jumping motions of the user are sensed indirectly via the deformation of the spring elements.
U.S. Pat. No. 7,008,359 B2 discloses an apparatus for balance exercises. It encompasses a base part, a support surface, and a central spring element that is arranged between the base part and support surface and is fixedly connected to each of them. The support surface can be tilted and rotated in relation to the base part, the spring element generating restoring forces that counteract those motions. The apparatus possesses an adjusting mechanism with which said restoring forces can be modified. The adjusting mechanism encompasses four wedge-like locking apparatuses that can simultaneously be shifted radially (relative to a central and vertical axis Z). When the locking apparatuses are shifted inward, the space for elastic deformation of the central spring element becomes smaller, bringing about an increase in the restoring force and at the same time a limitation of the maximum tilt angle.
EP 0 966 724 B1 discloses an apparatus for sensing weight displacements, rotational motions, and jumping motions of a user. A support surface is mounted on a base part, tiltably around two horizontal, mutually orthogonal spatial axes X and Y, as well as rotatably around a vertical spatial axis Z orthogonal to spatial axes X and Y and movably along said spatial axis Z. The restoring forces that counteract a tilt and a vertical motion of the support surface are generated by an air tube, and can be adjusted by modifying the inflation pressure in the air tube. The air tube is arranged between the base part and an intermediate part that is mounted nontiltably but rotatably relative to the support surface. A sensor apparatus senses the motions of the support surface and generates corresponding sensor signals.
All these balance boards have in common the fact that they comprise a support surface, tiltable on a base part, for the user's body, and a restoring apparatus for generating a restoring force counteracting the tilt. If the balance boards are designed to be used to control computer games, they furthermore possess a sensor apparatus that senses weight displacements on the support surface.
The disadvantage of the apparatus described in US 2008/0261696 A1 is that the tiltability of the support surface is so greatly limited that a tilt is barely perceptible by the user. This is disadvantageous because the user does not obtain direct feedback regarding the motions performed by him or her. Feedback instead occurs only indirectly via the respective computer program and the signal which is outputted again after processing the input signal. If, conversely, the support surface of the apparatus described in US 2008/0261696 A1 were to tilt perceptibly in the context of a weight displacement, the user would obtain direct physical feedback regarding the motions performed by him or her. The user would thereby be substantially better able to calibrate his or her weight displacements, which as a result would make a computer game easier to control.
A further disadvantage of the greatly limited tiltability of the support surface of the apparatus described in US 2008/0261696 A1 emerges when it is used to control computer games that simulate sports such as skateboarding, snowboarding, or surfing. In these sports, the corresponding items of sporting equipment (skateboards, snowboards, or surfboards) in reality execute pronounced motions, in which context the user obtains, by way of the change in the spatial position of the item, important feedback as to its interaction with the environment.
Because the support surface of the apparatus described in US 2008/0261696 A1 does not modify its spatial position in a manner similar to, for example, the item of sporting equipment that the apparatus represents in a computer game, the user does not obtain the impression that he or she is interacting, by way of the apparatus described in US 2008/0261696 A1, with the virtual environment of the computer game. This negatively affects the impression of a virtual reality, and disrupts the user's game experience.
A further disadvantage of the greatly limited tiltability of the support surface of the apparatus described in US 2008/0261696 A1 is lastly that this apparatus can be used to only a very limited extent as a training or rehabilitation device. The reason for this is that the strength and coordination of specific muscle groups such as, for example, the ankle musculature can be improved only when the user or patient is standing on a definitely tiltable support surface and must compensate for that tilt with his or her locomotor system.
A further disadvantage of the apparatus described in US 2008/0261696 A1 is that the restoring forces cannot be modified by the user. Given that the tiltability of the support surface of the apparatus described in US 2008/0261696 A1 is in any case very greatly limited, however, this disadvantage is acceptable, since the need for an adaptation of restoring forces increases only with an increasingly pronounced tiltability of the support surface. The reason is that as the tilting motions of the support surface become greater, it becomes that much more difficult for the user to maintain his or her balance when no restoring forces, or only small ones, are counteracting a tilt of the support surface.
The magnitude of the restoring forces experienced by a user as appropriate depends, however, not only on his or her skill and preferences, but also very substantially on his or her weight. In the context of a balance board conceived for the mass market, it would therefore be desirable if its restoring forces could be adapted both to the forces exerted on the balance board by a small child weighing 15 kg, and to the forces exerted on the balance board by a large adult weighing 150 kg.
The apparatus described in U.S. Pat. No. 7,008,359 B2 offers a definitely perceptible tiltability of the support surface, which is also absolutely necessary for the use, intended by the inventors, as a training and rehabilitation device. In the case of the apparatus described in U.S. Pat. No. 7,008,359 B2, the restoring forces can consequently be modified. The restoring forces are increased by the fact that the so-called locking mechanism decreases the space for an elastic deformation of the central rubber spring element, the result being to bring about a preload on the spring element.
A disadvantage of the apparatus described in U.S. Pat. No. 7,008,359 B2 is, however, that the increase in the restoring forces is accompanied by an increasing limitation of the tiltability of the support surface. It has already been mentioned, however, that certain training effects can be produced for the user only if he or she must compensate for pronounced tilting motions of a support surface. As a design constraint, therefore, not every user will be able to achieve the same training effect with this apparatus.
A further disadvantage of the apparatus described in U.S. Pat. No. 7,008,359 B2 is that the restoring forces cannot be modified independently of one another for different tilt directions. The central rubber spring element is indeed designed so that it generates smaller restoring forces in the context of a tilt around the longitudinal axis of the device than in the context of a tilt around the transverse axis. This takes into account the fact that the forces a user standing on the support surface is capable of exerting on the support surface by means of a weight displacement between his or her forefoot and heel are smaller than those produced by a weight displacement between his or her left and right foot, at least when the user is standing on the support surface with his or her feet comfortably at shoulder width.
But because the locking mechanism of the apparatus described in U.S. Pat. No. 7,008,359 B2 always engages simultaneously at four points on the central rubber spring element, and thus also simultaneously modifies the restoring forces in the context of a tilt around the longitudinal axis and a tilt around the transverse axis, the ratio of the restoring forces for the longitudinal and the transverse axis is defined as a result of the design and is not modifiable.
On the basis of experience, however, it is not the case that two users who prefer, for example, the same restoring forces in the context of a tilt around the transverse axis (i.e. in the context of a weight displacement between the left and right foot, and vice versa) will also always find the same restoring forces in the context of a tilt around the longitudinal axis (i.e. a weight displacement between the forefoot and heel) to be appropriate. This is especially not the case when these two users have feet of different sizes, since when the foot sizes are different, energy is introduced at different points, resulting in turn in non-identical lever ratios.
Optimally, however, it should be possible not only to modify the ratio between the restoring forces for the longitudinal axis and the transverse axis. For certain exercises, for example for rehabilitation in a context of unilateral injuries, it may be desirable for greater restoring forces to be generated with a displacement of weight onto the left foot than with a displacement of weight onto the right foot, and vice versa, or for greater restoring forces to be able to be generated with a displacement of weight onto the forefoot than with a displacement of weight onto the heel, and vice versa.
In the case of the apparatus described in EP 0 966 724 B1, the restoring forces can be modified with no limitation on the tiltability of the support surface, since here the increase in restoring force is achieved solely by way of an increase in the pressure in the air tube and not, as in the case of the apparatus described in U.S. Pat. No. 7,008,359 B2, by reducing the space for elastic deformation of the spring element.
The air cushioning technology of the apparatus described in EP 0 966 724 B1 also has disadvantages, however. In order for the air cushioning system not to have too highly progressive a spring characteristic, which would cause the cushioning to be perceived by the user as too hard, the air tube must have comparatively large dimensions. The components between which the air tube is arranged and against which it engages (which in EP 0 966 724 B1 are the base part and the intermediate part) must be designed to be similarly large. The result is large overall dimensions and heavy weight for the apparatus as a whole, making its handling in turn impractical. In addition, the comparatively high material usage has an unfavorable effect on manufacturing costs.
A further disadvantage is the fact that an accessory, for example an air pump with a pressure gauge, is needed in order to adapt the pressure in the air tube. This in turn increases the cost of the apparatus as a whole. In addition, a user may find that dealing with the accessory or filling the air tube is in itself inconvenient.
It is also the case that in the case of the apparatus described in EP 0 966 724 B1, the ratio of the restoring forces in the various tilt directions is defined in terms of physical design by the arrangement of the air tube, and is not modifiable. The disadvantages explained above with reference to U.S. Pat. No. 7,008,359 B2 are thus also relevant to EP 0 966 724 B1.
Yet another disadvantage arises when the apparatus described in EP 0 966 724 B1 is also used for computer simulation of certain sports such as snowboarding or surfing. Here a better impression of a virtual reality would be achievable if the return forces could, for example, be adjusted so that the support part is less easy to tilt forward than to tilt back, although this is also not possible with EP 0 966 724 B1.